1. Field of the Invention
The present invention relates generally to a process for the removal of carbonyl contaminants in hydrocarbon streams. More particularly the invention relates to the removal of carbonyl compounds from a stream containing at least aldehydes, ketones or esters. More particularly the invention relates to a removal process wherein the carbonyl compounds, including the aldehydes and ketones, undergo reactions in the presence of an acidic catalyst and at least, a part of the reaction products are adsorbed/absorbed on the catalyst.
2. Related Art
Linear olefins are isomerized to branched olefins in the presence of an acidic catalyst such as molecular sieves, silica-alumina, fluorinated alumina, etc. The tertiary olefins that are a product of the isomerization are useful as feed to a tertiary ether process or to an alkylation process.
When a stream containing both linear and branched olefins is fed to an etherification process the branched olefins preferentially react with an alcohol to produce the tertiary ether. In the case of isobutene and methanol the reaction product is methyl tertiary butyl ether (MTBE) and in the case of isopentene (isoamylene) and methanol the product is tertiary amyl methyl ether (TAME). Both ethers are useful as gasoline additives.
The unreacted linear olefins, either the normal butenes or normal pentenes, can be used in a cold acid alkylation process or may be isomerized to branched olefins and recycled back to the etherification process. In either case, the normal olefins from the initial etherification may contain trace amounts of the unreacted alcohol which act as catalyst inhibitor in the isomerization process or consume acid in cold acid alkylations. Aldehydes and ketones may be contained in other feedstreams to a skeletal isomerization process. For example, the C.sub.5 stream from a Fischer-Tropsch synthetic fuel process contains small amounts of acetone, propionaldehyde, methyl ethyl ketone and butylaldehyde as well as alcohols. These carbonyl compounds render molecular sieve skeletal isomerization catalysts, such as zeolites, e.g., ferrierite, useless after only a few hours on stream. In an integrated process for etherification and isomerization as disclosed in U.S. Pat. Nos. 5,210,327 and 5,276,212, the linear olefins are treated to remove the alcohol, water and nitrogen compounds prior to the isomerization. The alcohol and nitrogen compounds are removed by adsorption on zeolitic molecular sieves by a process disclosed in U.S. Pat. No. 4,814,517. Any acetone or acetonitrile in the feed is removed by a water wash prior to the etherification.